Zinc Pills May Shorten Colds, Analysis Suggests

But, benefits are slight and side effects are reported, researchers say

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By Steven Reinberg
HealthDay Reporter

MONDAY, May 7 (HealthDay News) -- Those suffering from the common cold will try almost anything to relieve their symptoms, but a cure has yet to be found.

A new Canadian analysis has revealed that zinc tablets may help patients suffer a little less, but side effects are common.

"Although it is possible that oral zinc preparations impact symptoms of the common cold, there is currently insufficient evidence to recommend its use in children and only a weak rationale for use in otherwise healthy adults," said lead researcher Dr. Michelle Science, of the Hospital for Sick Children in Toronto. "The decision to use zinc should take into consideration the questionable benefits balanced against the potential adverse effects."

The report was published in the May 7 edition of the Canadian medical journal CMAJ.

For the study, Science's team looked at the findings of 17 randomized trials that included more than 2,100 patients. In these trials, patients were given either zinc or placebo tablets to see if there was a difference in outcome.

The researchers found that people who took zinc saw a significant reduction in both cold symptoms and the duration of those symptoms. Higher doses of zinc worked better than low doses, they noted.

There was evidence, although weak, that zinc relieved symptoms after a week. There was no difference in symptoms between those taking zinc and those taking placebo at three days, however.

Although zinc seemed to work in adults, it appeared to have no effect on children, Science's group found.

"We found that evidence of benefit from zinc was limited to otherwise healthy adults," Science said. "But even in this group, uncertainty remained about its clinical benefits."

People taking zinc also were more likely to have side effects, including bad taste and nausea, than those taking placebo, the researchers noted.

The decision to use zinc also may be affected by how the tablet is used, Science said. Some people may not like the idea of using zinc lozenges every two hours, she said.

Results of earlier studies were inconsistent as to whether zinc reduced cold symptoms and duration, the researchers noted.

Dr. Robert Schwartz, chairman of family medicine at the University of Miami School of Medicine, said that "this has been a homeopathic remedy that's been around for a while, but there really aren't a lot of studies that demonstrate it helps a cold. There isn't a lot of clinical-based data to show it's effective."

Schwartz said he tries to explain to patients how viruses work, and what will work and what won't. There are medicines to treat fever and aches and congestion that come with a cold, but there is no cure. Usually a cold passes within a week or so.

"But we live in a world were people want an instant cure, and people want to get better immediately," he said.

When it comes to zinc, Schwartz tells patients if they want to try it, it's not poisonous, but there is no evidence that it will improve a cold any faster than doing nothing.

As for the side effects, Schwartz said a bad taste in the mouth and nausea are what usually accompanies digesting any heavy metal. "These are typical side effects," he said.

More information

For more on colds, visit the U.S. National Library of Medicine.

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